DESCRIPTION During the development of the Arabidopsis flow, patterns of cellular proliferation and differentiation are orchestrated by a set of regulatory genes whose individual identities and mechanisms of action are incompletely understood. The long-term research goal of this proposal is to understand the molecular regulation of cellular proliferation and differentiation during Arabidopsis ovule and flower development. A newly identified gene, ENHANCER OF AINTEGUMENTA (ENA), plays an important role in ovule phenotypes of the ena mutant, alone and in combination with regulators that interact genetically; and to isolate the ENA gene to discern its molecular nature. To achieve aim I, ovule and flow development will be characterized in various genetic backgrounds by scanning electron microscopy, confocal microscopy, thin section analysis and in situ hybridization. These experiments will shed light on functional interactions underlying ovule and flower development. To molecularly isolate the ENA gene, a map based cloning approach will be used. This approach will rely on existing physical and genetic maps and the extensive database resources available. The molecular cloning of ENA will enable the analysis of ENA expression patterns and an investigation of the effects of ENA ectopic expression on Arabidopsis development. Molecular conservation between Arabidopsis and Homo sapiens indicates that studies into floral organ development can illuminate basic molecular mechanisms that are relevant to the study of human disease states. Additionally, by illustrating general principles of functional redundancy and method to evaluate genetically redundant genes, the proposed research can strengthen genome- and proteome-based efforts to understand the etiology of human disease.